CGRG Bibliography of Canadian Geomorphology
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Author : Adams, J.; Bent, A.L.; Ma, S.; and McCormack, D.
Date : 2002.
Title : New insights into southeastern Canadian earthquakes.
Publication : American Geophysical Union 2002 Fall Meeting, Moscone Center, San Francisco, California, 6-10 December 2002.
Issue :
Page(s) :
Abstract
Since the Saguenay earthquake of 1988 four moderate magnitude earthquakes - 19901019 Mont-Laurier (Mw 4.5, depth=13 km), 19971106 Cap-Rouge (Mw 4.5, z=22), 19990316 Cote-Nord (Mw 4.5, z=19) and 20000101 Kipawa (Mw 4.7, z=12) - have occurred in southeastern Canada (together with three adjacent US events of similar size: 1998 Pymatuning, 2002 Au Sable Forks and 2002 Evansville). Improvements to seismograph coverage (particularily installation of digital broadband 3-cpt sensors) have provided higher quality data and allowed more detailed modelling of their rupture properties. Aftershock studies and seismotectonic investigations have provided new insights (we thank Maurice Lamontage for his contribution to these studies). We sumarize the published conclusions from the four earthquakes together with new surface-wave deduced parameters. These were typically thrust faulting events in response to NE-directed compression, and can be related to broad seismotectonic features in their vicinity, though seldom to specific faults. The study of these events requires not only the interpretation of time series data but also consideration of the spectral content of the energy received. A major constraint in studying these and smaller earthquakes is poor knowledge of the crustal properties (velocity layering and attenuation as a function of frequency) and often a disconcerting uncertainty in starting parameters (focal mechanism, depth, moment, stress drop, number of sub-events, rupture velocity) together with the potential for significant trade-off errors (e.g. between moment and attenuation). Such detailed studies can be very rewarding but extremely time consuming. Taken with the results for the 1988 Saguenay (Mw 5.9, z=29), 1989 Ungava (Mw 6.3, z$<$5) and a dozen Mw=4 events we conclude that the stable craton is seismogenic from the surface to $>$30 km. Both Saguenay and Ungava earthquakes had Mw 4 1/2 foreshocks, suggesting that the rapid study of future moderate events may be fruitful.
Bibliography of Canadian Geomorphology